我是Android开发的新手。这是一个相机应用程序，它没有编译错误。但是当它在模拟器上运行时它将无法工作。它给出了“遗憾的预览已停止”。然后我在具有“android 2.3.6”操作系统的手机上测试它，然后也出现错误“应用程序预览（进程com.example.preview）意外停止。请再试一次”< / p>
MainActivity.java
package com.rrd.perview;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import android.hardware.Camera;
import android.hardware.Camera.PictureCallback;
import android.hardware.Camera.ShutterCallback;
import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
//import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.FrameLayout;
public class MainActivity extends Activity {
private static final String TAG = "CameraDemo";
Camera camera;
Preview preview;
Button buttonClick;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
preview = new Preview(this);
((FrameLayout) findViewById(R.id.preview)).addView(preview);
buttonClick = (Button) findViewById(R.id.buttonClick);
buttonClick.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
preview.camera.takePicture(shutterCallback, rawCallback, jpegCallback);
}
});
Log.d(TAG, "onCreate'd");
}
ShutterCallback shutterCallback = new ShutterCallback() {
public void onShutter() {
// TODO Auto-generated method stub
Log.d(TAG,"onShutter'd");
}
};
PictureCallback rawCallback = new PictureCallback() {
public void onPictureTaken(byte[] data, Camera camera) {
// TODO Auto-generated method stub
Log.d(TAG, "onPictureTaken - raw");
}
};
PictureCallback jpegCallback = new PictureCallback() {
public void onPictureTaken(byte[] data, Camera camera) {
// TODO Auto-generated method stub
FileOutputStream outStream = null;
try{
outStream = new FileOutputStream(String.format("/sdcard/%d.jpg", System.currentTimeMillis()));
outStream.write(data);
outStream.close();
Log.d(TAG, "onPictureTaken - wrote bytes: " + data.length);
}catch(FileNotFoundException e){
e.printStackTrace();
}catch(IOException e){
e.printStackTrace();
}finally{
}
Log.d(TAG, "onPictureTaken - jpeg");
}
};
}
Preview.java
package com.rrd.perview;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
//import android.R.color;
//import android.R.string;
import android.annotation.TargetApi;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.hardware.Camera;
import android.hardware.Camera.PreviewCallback;
import android.hardware.Camera.CameraInfo;
import android.os.Build;
//import android.os.Environment;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
class Preview extends SurfaceView implements SurfaceHolder.Callback{
private static final String TAG = "Preview";
SurfaceHolder mHolder;
public Camera camera;
//@SuppressWarnings("deprecation")
Preview (Context context){
super(context);
mHolder = getHolder();
mHolder.addCallback(this);
//mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
@TargetApi(Build.VERSION_CODES.GINGERBREAD)
@Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
Camera.open(CameraInfo.CAMERA_FACING_BACK);
try {
camera.setPreviewDisplay(holder);
camera.setPreviewCallback(new PreviewCallback() {
public void onPreviewFrame(byte[] data, Camera camera) {
// TODO Auto-generated method stub
FileOutputStream outStream = null;
try{
outStream = new FileOutputStream(String.format("/sdcard/%d.jpg",System.currentTimeMillis()));
outStream.write(data);
outStream.close();
Log.d(TAG,"onPreviewFrame - wrote bytes: "+ data.length);
} catch(FileNotFoundException e){
e.printStackTrace();
} catch(IOException e){
e.printStackTrace();
}finally{
}
Preview.this.invalidate();
}
});
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
camera.stopPreview();
camera = null;
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// TODO Auto-generated method stub
Camera.Parameters parameters = camera.getParameters();
parameters.setPreviewSize(w, h);
camera.setParameters(parameters);
camera.startPreview();
}
public void drow(Canvas canvas){
super.draw(canvas);
Paint p = new Paint(Color.RED);
Log.d(TAG, "drow");
canvas.drawText("Preview",canvas.getWidth()/2,canvas.getHeight()/2, p);
}
}
activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<FrameLayout android:id="@+id/preview"
android:layout_weight="1"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
</FrameLayout>
<Button android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/buttonClick"
android:text="Click" android:layout_gravity="center">
</Button>
</RelativeLayout>
的AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.rrd.perview"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<uses-permission android:name="android.permission.CAMERA"/>
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.rrd.perview.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
logcat的
11-20 05:02:23.974: D/CameraDemo(1075): onCreate'd
11-20 05:02:24.804: D/AndroidRuntime(1075): Shutting down VM
11-20 05:02:24.804: W/dalvikvm(1075): threadid=1: thread exiting with uncaught exception (group=0xb1b0ab90)
11-20 05:02:24.884: E/AndroidRuntime(1075): FATAL EXCEPTION: main
11-20 05:02:24.884: E/AndroidRuntime(1075): Process: com.rrd.perview, PID: 1075
11-20 05:02:24.884: E/AndroidRuntime(1075): java.lang.NullPointerException
11-20 05:02:24.884: E/AndroidRuntime(1075): at com.rrd.perview.Preview.surfaceCreated(Preview.java:43)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.view.SurfaceView.updateWindow(SurfaceView.java:572)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.view.SurfaceView.access$000(SurfaceView.java:86)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.view.SurfaceView$3.onPreDraw(SurfaceView.java:175)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:847)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1869)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5582)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.view.Choreographer.doCallbacks(Choreographer.java:562)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.view.Choreographer.doFrame(Choreographer.java:532)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.os.Handler.handleCallback(Handler.java:733)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.os.Handler.dispatchMessage(Handler.java:95)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.os.Looper.loop(Looper.java:137)
11-20 05:02:24.884: E/AndroidRuntime(1075): at android.app.ActivityThread.main(ActivityThread.java:4998)
11-20 05:02:24.884: E/AndroidRuntime(1075): at java.lang.reflect.Method.invokeNative(Native Method)
11-20 05:02:24.884: E/AndroidRuntime(1075): at java.lang.reflect.Method.invoke(Method.java:515)
11-20 05:02:24.884: E/AndroidRuntime(1075): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
11-20 05:02:24.884: E/AndroidRuntime(1075): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
11-20 05:02:24.884: E/AndroidRuntime(1075): at dalvik.system.NativeStart.main(Native Method)
11-20 05:03:03.864: I/Process(1075): Sending signal. PID: 1075 SIG: 9
答案 0 :(得分：0)
你的问题是什么？你都尝试了些什么？ 记住几点要点：
，你这样做：
Camera.open（CameraInfo.CAMERA_FACING_BACK）;
然后你正在使用未初始化的相机对象！将上述内容更改为：
camera = Camera.open(CameraInfo.CAMERA_FACING_BACK);
并检查RuntimeException，如果打开相机失败，可能会得到。
请查看有关相机控制的Android培训课程：
http://developer.android.com/training/camera/cameradirect.html